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The number of phage in a culture of bacteria/phage can be used as a measure of t

ID: 13664 • Letter: T

Question

The number of phage in a culture of bacteria/phage can be used as a measure of the viability of bacteria. This is useful to screen 1) antimycobacterial drugs, and 2) bacterial susceptibility to antibiotics. Explain how phage are useful to the screen. Why not just use the bacteria as a direct measure?

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you have 10ul of asolution of DNA at a concentration of 327 ng/ul. How many ng of DNA do you have?

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How many ul of DNA do you need to pipet to obtain 125 ng of DNA for use in an experiment??

Explanation / Answer

The number of phages present in a culture of bacteria and phages indicate whether the bacteria can resist the invasion of phages. If the number of the phages on the plate is more than the number of phages in the original sample, we can deduce that the bacterial cells have been attacked and lysed and used for the multiplication of the phages. IF the number remains the same, it indicates that the bacterial cells used are not specific for that phage. --------------------------------------------- The phages are useful in the screen as we cannot visually identify whether a bacterial cell is viable or not. There are many cells in a culture and dead cells would be difficult to spot. When phages infect cells, the lysed cells appear as plaques which is easy to spot. --------------------------------------- DNA concentration per l is 327 ng. 10 l of the solution would contain 327 x 10 = 3270 ng of DNA. ---------------------------------------- 327 ng of DNA is present in 1 l of solution. 125 ng of DNA would be present in 125/327 = 0.38 l of solution.